Vegetables are the fresh and edible portions of the herbaceous plants. They classified as seasonal vegetables but they also classified as root, tuber, shoot, flower, fruit and leafy on the base of mode of consumption. Each of the categories mentioned above have its own role in human body. They play a vital role in human health due to their higher nutritional values. They are major source of macro and micro nutrients which required by the human body for optimal functioning. They are not only involved for normal body functioning but they also disease preventive in nature. Heavy metals get entry through different routes and accumulate in edible and inedible portions of the vegetables in quantity enough to cause clinical problems to humans and animals. This study was designed to assess the level of heavy metals in vegetables in different districts of Punjab.
Heavy metal is defined as metallic element usually toxic in nature with high density and atomic weight. As they are toxic in nature they accumulate in different parts of the vegetables and lead to several health complications in humans. Some of these metals are of nutritionally important for human health in small quantities and referred as trace elements which include zinc, iron, copper etc. They are among the major toxicants in vegetables which may cause chronic diseases in the kidney and liver of humans and causes disruption of numerous biochemical processes leading to cardiovascular, nervous, kidney and bone diseases. Open crown vegetables like cauliflower have more chances of infestation in suburbs due to waste water irrigation as compared to intact skin vegetables especially grown away from suburbs. Moreover, vegetables treated under clean sanitary conditions can have low levels of heavy metals as compared to the untreated ones.
There are different sources of heavy metals which include waste water irrigation, industrial waste water and soil pollution which associated with industrialization and agricultural activities such as atmospheric deposition, waste disposal, waste incineration, vehicle exhaust, fertilizer application and long term application of sewage sludge in agriculture land. Waste water contains sufficient amount toxic heavy metals which cause clinical problems.
In the present study two vegetable cauliflower (Brassica oleracea) and carrot (Dascusorrota) were collected from suburbs of Lahore. While samples of cauliflower were include from various districts of Punjab. The heavy metals Pb, Zn, Cr, Ni, Ca, Mg, K and Na were determined in cauliflower and carrot from suburbs; While Pb, Zn, Cr and Ni were observed in cauliflower from various districts of Punjab. Digested vegetable samples were analyzed through Atomic Absorption Spectrophotometer.
The highest levels for heavy metals (ppm) Lead, Zinc, Chromium and Nickel in Lahore for cauliflower and carrot was (2.2267±0.0251, 2.2317±0.0076), (5.7100±0.0360,5.0333±0.2516), (1.1133±0.1154, 1.7333±0.0763), (2.466±0.1040, 2.4000±0.3605) respectively. There was a significant difference in both vegetables. Difference in concentration in both vegetables is due to the surface area of both vegetables as cauliflower has large surface area as compared to carrot.
The highest levels for heavy metals (ppm) Lead, Zinc, Chromium and Nickel in Gujranwala for cauliflower was (2.3266±0.0145, 4.5966±0.0152, 0.9333±0.0152, 2.2467±0.0251) respectively.
The highest levels for heavy metals (ppm) Lead, Zinc, Chromium and Nickel in Sheikhupura for cauliflower was (1.9000±0.0200, 6.043±0.0513, 0.933±0.0152, 2.490±0.0100) respectively.
The highest levels for heavy metals (ppm) Lead, Zinc, Chromium and Nickel in Faisalabad for cauliflower was (1.928±0.0104, 5.736±0.0156, 1.193±0.0057, 2.476±0.152) respectively.
The highest levels for heavy metals (ppm) Lead, Zinc, Chromium and Nickel in Kasoor for cauliflower was (1.900±0.0200, 6.043±0.0513, 0.933±0.0152, 2.490±0.0100) respectively.
Each of the city have different concentration of the metals, several reasons for this variation which include medium on which these vegetables are growing, water used for irrigation, application of agricultural products, poor agricultural practices and post-harvest treatment which include harvesting procedure, washing of vegetables with unsafe water and transfer from long rooted areas. Uptake behavior of these metals and minerals by vegetables also affect it. The transfer factor (TF) of different heavy metals from soil to vegetation is one of the key components of human exposure to metals through the food chain. The highest TF valueis found for Zn because Zn is more mobile in nature. This study will provide a baseline data and there is a need for intensive sampling of the same for quantification of the results. Soil, plant and water quality monitoring, together with the prevention of metals entering the plant, is a prerequisite in order to prevent potential health hazards of wastewater irrigation. By using good agricultural practices including use of less agricultural chemical products and sewage water should be used after proper treatment.